SOHC.co.uk Forums > CB750

Flat spot 65-70mph

<< < (3/4) > >>

leonardo269:
Hi,
    I checked my timing yesterday and found out it was quite a bit out.

it needed to be set at full advance (3000rpm) and I think I must of set it up at tickover. It just shows that you can never be too experienced to make a mess of things. :blush:

If it ever stops peeing down I must get a chance to test it out.:S

uk_kev:
so is it tested, and if so how is it now?

leonardo269:
Hi there,

I think I have now hit on the problem (or problems).

I stripped the carbs last night and recovered a slither of red material (looks like a bit of a fibrewasher (approx 1.5mm x 0.5mmx 0.5mm) in alongside carb2 float valve.

Also the push-rod of the accelleration pump (on carb 2 as well) was feeling decidedly siezed, so I stripped & cleaned it.

All the float heights seem OK

The main jets are all clear, they are 120

The float bowl gasket seals look a bit flat so I am replacing them. - Does anyone know if these can be obtained separatley (or am I going to be mugged for a \"carb kit\" at

leonardo269:
OK - Time for a bit of an update on the K7 carb issues.

The carbs have been rebuilt with 4 new float valves and all the float heights where set to 12.5mm. my Haynes manual is a bit scarce on where the measurement actually takes place, as the floats taper down the further away from the fulcrum they get . I have assumed it is in the middle of the carb, in-line with the main jet. If anybody knows any different then please let me know.

I also noted that the spring on the accelleration pump was not strong enough to move the pushrod when the throttle was turned so I have replaced it with a stronger spring that I had lying around.

Better!

I then fitted the original Honda air filter.

Holy Sh*t - Much better! :ohmy:

I still get a slight hesitancy aorund 70mph (it basically feels like I am starting to run out of petrol), but overall the power is way up on what it was.

I am going to set the slow running mixtures with a clourtune tomorow and re-check with the vacuum guages to see if this gets rid of the problem.

I also have some 122.5 main jets that may get a test if the above doesn't work (and if I feel like poisoning myself with the smell of petrol again).

The only other option is to try standard 115 jets (Can anyone report sucessfully using them with a motad 4-1 exhaust?)

Cheers,

Ray

leonardo269:
Hi again,

I Set up the carb mixture and synced the carbs today.

It goes like a rocket now. :woohoo:

I hope my meddling exploits can be of assistance to others who encounter similar problems in the future.

Thanks to eveyone who chipped in with ideas.

Cheers,

Ray

Navigation

[0] Message Index

[#] Next page

[*] Previous page